There exist in the art methods of detecting simple peptides. However, methods to determine the effective plasma concentration of mixtures of peptides as a group, rather than for individual peptides with a defined amino acid sequence, are complicated by the heterogeneity of the peptides to be detected. For example, random sequence polymer (RSP) compositions comprise a complex mixture of amino acids that have been randomly incorporated into peptide chains. RSP compositions are defined according to the identity and ratio of amino acids, not according to a defined sequence. Given this diversity, improved methods for evaluating the consistency and composition of these RSP compositions through multiple manufacturing preparations are needed. Determining the in vivo status of an RSP composition has immunologic significance because, depending on the route and/or frequency of administration and the serum proteins that bind the RSP composition, a mixture can invoke primarily inflammatory (TH1 type) or primarily regulatory (TH2 type) responses, leading to variations in pharmacokinetic and pharmacodynamic effects in the subject. More rigorous design and consistent administration of an RSP composition may increase the therapeutic efficacy, or reduce the potential for adverse inflammatory responses.
Thus, there is a need for methods of quantitative analysis of RSP compositions, e.g., to assist the in vivo evaluation of such mixtures and to determine the suitable amount and means of administration for therapeutic purposes.